Optimum water use efficiency of crop plants is necessary to obtain maximum land use. Smooth bromegrass is the best cultivated forage in South Dakota, producing abundant forage in spring and tending to become dormant during the summer. It is suggested that the water use efficiency of this grass could be increased by selecting for a variety with improved regrowth in the summer so that it could continue to provide forage during the entire season. Plants with outstanding regrowth characteristics were selected from two irrigated nurseries. Mean measurements such as yield regrowth, net carbon dioxide exchange and height were significantly different between genotypes. Such measurements usually correlated positively with growth potential. Efficiency of photosynthesis was measured by net carbon dioxide exchange and was unrelated to ability of plants to grow back after cutting.